1. Technical Field
The present invention relates generally to a method and apparatus for use in detecting focal accumulation of radiopharmaceutical agents within an arterial lumen. More particularly, the present invention provides a miniaturized fiber optic-coupled scintillator attached to an external image processing unit for detecting accumulated radiopharmaceutical agents within a blood vessel. Optionally, the apparatus may be fitted with a system for minimizing the accumulated plaque.
2. Summary of Related Art
Atherosclerosis is one of a handful of conditions in which a thickening or hardening of the walls of arterial vessels occurs, the other conditions being Monckeberg's sclerosis (deposition of calcium salts in the muscular wall of arteries) and arteriolosclerosis (thickening of arterioles). Atherosclerosis is generally multifocal. The lesion or atherosclerotic plaque--comprises a mass of fatty material. This material is associated with fibrous connective tissue and frequently includes deposits of calcium salts and other residual material. These plaques initially begin in the intima of the affected vessel but may eventually extend into the media of the vessel.
In developed countries, atherosclerosis is frequently seen in all but the youngest of people, although genetic predispositions play an important role in the course of the disease. The damage caused by atherosclerosis varies. If a medium-sized blood vessel such as a coronary artery is involved, the plaque build-up may restrict blood flow or may stop it altogether in more extreme cases. Thrombus formation may also result on the roughened area which results from the built-up plaques. Of considerable concern is the possibility of the soft lipid portion of the plaque breaking away and being deposited in a narrow vessel, frequently resulting in a stroke. Relief of focal high-grade obstruction may control symptoms, but the patient usually is left with numerous nonobstructive plaques prone to later rupture and infarction.
While conventional imaging and detection of coronary atherosclerosis by contrast angiography or intravascular ultrasonography provides valuable anatomic detail, it does not characterize the underlying biological processes which may lead to plaque expansion or rupture with attendant acute coronary syndromes. In particular, available imaging and detection modalities have limited ability to predict the site of future myocardial infarction and have demonstrated an inability to differentiate between active (unstable) and inactive (stable) plaque sites. While percutaneous coronary revascularization provides excellent symptom relief in selected patients with obstructive coronary artery disease, it has been difficult to demonstrate that percutaneous revascularization reduces the incidence of future myocardial infarction.
While all plaque build-up on vessel walls is to be of concern, it is impractical to resolve each plaque site throughout the affected individual's vascular system. Atherosclerotic plaques are characterized by mural inflammatory infiltrates which may contribute to their instability. Noninvasive imaging and detection of mural inflammation in atherosclerotic arteries is hampered by small tissue mass, high background activity from visceral and blood pool radiotracer, poor spatial resolution, poor correlation with local anatomy, and, in coronary arteries, by cardiac motion artifact. It is accordingly desirable to treat the most potentially dangerous plaques, or the so-called "active" plaques which are metabolically active. It is this form of plaque that cause the most trouble to the body in the form of coronary artery disease and atherosclerosis because of their tendency to let loose some of the lipid material from the site causing thrombosis. If loosened, this material could travel through the vascular system causing a coronary attack if in the region of the heart, a stroke if in the region of the brain, or an occlusion of a vessel if in the leg. The difficulty is in identifying the stable plaque from the unstable plaque and providing a method of treatment.
Accordingly, a method to identify the active, unstable, or "vulnerable" coronary atherosclerotic plaques might have broad clinical utility and remains wanting in the art.